The optical recording media are in widespread use, generally due to its superior characteristics such as large recording capacities, and noncontact recording or reproduction. In the write-once optical discs such as WORM, CD-R, DVD±R, and the like, recording is carried out by focusing the laser light on a minute area of the recording layer to change properties of the optical recording layer, while reproduction is performed based on a difference in intensities of light reflected from the recorded area and non-recorded area.
Presently, in the optical discs mentioned above, the wavelength of a semiconductor laser used for recording and reproduction is between 750 and 830 nm for CD-R and between 620 and 690 nm for DVD-R. However, in order to realize further increase in capacity, an optical disc which uses short-wavelength laser light is being explored. For example, one which uses light of wavelength between 380 and 420 nm as the recording light is under study.
In an optical recording medium for the short-wavelength recording light, various compounds are used to form the optical recording layer. For example, reported are in Patent Document 1 a hemicyanine dye, in Patent Document 2 a trimethine compound, in Patent Document 3 a porphyrin compound, and in Patent Document 4 a monomethine cyanine dye which has a specific structure. However, as an optical recording material used to form an optical recording layer, these compounds have problems that their absorption wavelength characteristics are not necessarily suitable or that they do not have excellent recording characteristics.    Patent Document 1: Japanese Patent Laid-Open Publication No. 2001-342365    Patent Document 2: Japanese Patent Laid-Open Publication No. 2004-98542    Patent Document 3: Japanese Patent Laid-Open Publication No. 2005-59601    Patent Document 4: International Publication No. WO/01/044374